The accumulation of dental calculus and its precursor, dental plaque, on tooth surfaces is a common dental problem. Dental calculus occurs because of the interaction between bacterial plaque and the host site. Dental calculus occurs both on visible surfaces of the tooth as well as hidden surfaces, such as the subgingival surface of the tooth and ultimately the root within periodontal pockets.
Calculus is essentially mineralized calcified plaque. Mature calculus consists of approximately 15%-20% organic material, and the remainder is mineral salts. The minerals, predominantly calcium and phosphates, are deposited in an organic matrix. The mineral content of calculus spans a wide range of components, from hydroxyapatite, to magnesium, potassium and trace components such as fluoride, zinc and strontium. Differences in the organic and inorganic composition of saliva and crevicular fluids or inflammatory exudates in contact with supragingival and subgingival plaque, respectively, account in large part for notable differences in the types of calculus which form in the supra- or subgingival environment.
Periodontal therapy is based upon the daily removal of bacterial plaque by the patient, and the removal of plaque, calculus and other oral debris by the periodontal therapist. The success of therapy, therefore, is dependent upon the identification and thorough removal of plaque and calculus and associated root contaminants. This is usually accomplished through a variety of different procedures, such as scaling and root planing, or through periodontal surgical procedures.
Dental calculus and other contaminants are currently identified through a variety of means. Plaque and dental calculus located on visible surfaces of the tooth can usually be seen quite easily during a dental examination. However, subgingival plaque and calculus in the periodontal pocket can be identified only by probing and exploration of the periodontal pocket by the therapist using various manual instruments. This process is laborious, and it is complicated by a great variation in local anatomy of the periodontium. Also, conventional tactile detection by hand probing is subject to limitations and error. Calculus may be present but go undetected, thus untreated. Conversely, false-positive diagnoses may lead to execution of unwarranted and costly removal procedures. Natural anomalies of teeth sometimes present difficulty to tactile probing. Practitioner time and effort may be wasted on asserting the nature of a questionable source and trying to remove it.
Detection of subgingival plaque and calculus becomes even more difficult as the severity of periodontal disease increases--a situation that makes detection of plaque and calculus even more important. Increasing periodontal disease and the resulting deepening in the periodontal pocket not only affect the ability to identify the plaque and calculus, but they also exert a profound effect upon the ability to remove these deposits by instrumentation. An additional complication is the fact that dental calculus may be deposited in areas of reabsorption of the root surface. Current methods of detection do not adequately differentiate between calculus and root roughness which has no clinical significance. Detection of subgingival calculus by nontactile means, such as by the use of X-rays, is also inadequate.
It has been claimed that dental caries can be detected optically. For example, Alfano U.S. Pat. Nos. 4,479,499 and RE 31,815 disclose a method and apparatus for detecting caries by illuminating a potential caries site with monochromatic light, and visible light emitted from the site is examined to provide an indication of the presence of caries at the site. Ingmar U.S. Pat. No. 4,515,426 similarly discloses a device for optically detecting caries in which a site is illuminated by a light having a predetermined wavelength or range, and the luminescent properties of light emitted at the site are examined to detect the presence of caries. Alfano U.S. Pat. No. 4,930,516 et al. discloses a method for detecting cancerous tissue using an optical technique similar to the technique used to detect caries in U.S. Pat. No. 4,479,499. Kittrell U.S. Pat. No. 4,718,417 et al. discloses a method of diagnosing arterial plaque in which light having a wavelength of about 480 nm is conducted through an optical fiber to an arterial site, and scattered light and fluorescence light from the site are returned through the optical fiber where they are analyzed to determine the presence of arterial plaque at the site.
An article by R. R. Alfano et al. entitled Medical Diagnostics: A New Optical Frontier in the Dec. 1985 edition of PHOTONICS SPECTRA, describes the use of luminescence spectroscopy to diagnose a variety of abnormal human conditions including tooth decay, cancer, and arteriosclerosis.
An article by J. Brinkmen et al. entitled Optical Quantitation of Natural Caries in Smooth Surfaces of Extracted Teeth in a 1988 edition of BASIC SCIENCES describes a system for optically detecting caries by separately illuminating a carious and a non-carious region of a tooth and comparing the light reflected from each region.
An abstract of a conference presentation by J. J.ten Bosch et al. given at the Jul. 3-6, 1985 conference of the Congress of European Organization for Caries Research in Stenungssund, Sweden and published in CALCIFIED TISSUE ABSTRACT, vol. 19, no. 2, p. 115, describes a luminescence technique for detecting caries.
An abstract of an article by J. J.ten Bosch et al. in 6 Swedish Dental Journal 1-7 (1982) entitled Long-Wavelength Fluorescence of Bovine Tooth Components published in ABSTRACTS FROM THE 32ND ORCA CONGRESS no. 106 also describes a luminescence technique for detecting caries.
The above-described prior art devices and publications have a number of features in common. First, they illuminate the site with monochromatic or narrow band light. Second, the light returned from the site is analyzed by measuring its amplitude at two wavelengths. Finally, none of the prior art patents and publications even recognize that dental plaque or calculus can be detected optically based on the luminescence properties of the deposit.
A sensor that could optically detect plaque and calculus would remove the uncertainty of tactile probing and would greatly increase the efficiency and effectiveness of basic dental care.